title: On the mechanism of recombination hotspot scanning during double-stranded DNA break resection.
abstract: Double-stranded DNA break repair by homologous recombination is initiated by resection of free DNA ends to produce a 3'-ssDNA overhang. In bacteria, this reaction is catalyzed by helicase-nuclease complexes such as AddAB in a manner regulated by specific recombination hotspot sequences called Crossover hotspot instigator (Chi). We have used magnetic tweezers to investigate the dynamics of AddAB translocation and hotspot scanning during double-stranded DNA break resection. AddAB was prone to stochastic pausing due to transient recognition of Chi-like sequences, unveiling an antagonistic relationship between DNA translocation and sequence-specific DNA recognition. Pauses at bona fide Chi sequences were longer, were nonexponentially distributed, and resulted in an altered velocity upon restart of translocation downstream of Chi. We propose a model for the recognition of Chi sequences to explain the origin of pausing during failed and successful hotspot recognition.
authors.affiliation: Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, 28049 Cantoblanco, Madrid, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Carrasco
authors.forename: Neville S
authors.initials: NS
authors.lastname: Gilhooly
authors.forename: Mark S
authors.initials: MS
authors.lastname: Dillingham
authors.forename: Fernando
authors.initials: F
authors.lastname: Moreno-Herrero
mesh_terms: D004247:DNA / Q000235:genetics*; D004249:DNA Damage; D011995:Recombination, Genetic
chemical_list: D004247:DNA
keywords: DNA-end processing; protein motor; protein–DNA interactions; real-time measurements; single molecule biophysics